As to your first comment about stat requirements on gear it's covered
More specifically it's the whole reason Determination exists.On the Prairie Tree
Brush Fire will be a long duration. I've also thought about it spreading but I'll have to run that by DG.
Dust Storm might be weak I don't know. Blind is a pretty powerful effect and considering this will be an AoE with a duration to it that causes blind when creatures enter it and also blocks LOS I'm inclined to think the utility of this in a fight will make it worth casting even if it doesn't deal damage. If not some damage can be added to it later on.
Don't discount Stride. Speed is one of the most powerful effects in the game even if it is 'just' movement speed. In fact I may move this ability down to the second or third tier (but that might make the second tier to light on damage talents). Also this will constantly drain stamina while active assuming Yufra doesn't mind me stealing that idea
On Forest being OP
This will all depend on the numbers. I think the effects are pretty well balanced with Desert being on the weaker side of the three. On the other hand there's been a lot of times I wished I could toss an illuminate down a hall and blistering sun lets you do just that, plus it's a generic talent >.> Also if I was going for a melee build rather then a caster build desert sting is an automatic poison attack that again doesn't cost class talents. Maybe Snake Charmer should be tier 1 or something else entirely it's the most meh of the talents.
Also none of this is set in stone so if anyone has good ideas for these trees, even for talent slots that are already filled, please post